1. Field of the Invention
The present invention relates to production control systems and integrated production control systems and in particular relates to a production control system and an integrated production control system that learn to minimize power consumption for production in a factory with a plurality of machines and an air conditioner, while satisfying temperature requirements inside the factory and product delivery deadlines.
2. Description of the Related Art
Factories are commonly equipped with a plurality of machines (e.g., machine tools) and, in the case of high precision processing, air conditioning (an air conditioner) is provided so as to control environmental conditions inside the factory because the temperature in the factory affects processing accuracy. Production at a factory is dictated by a production plan, and, to produce the products dictated by the production plan within a dictated delivery deadline, the running status and processing conditions of a plurality of machines are controlled, and the running status of the air conditioner is also controlled so as to achieve temperature conditions (temperature and uniformity) inside the factory required for the processing.
The time for proceeding from one processing step to the next in a production process of a product is called takt time, which is an index extensively used in production management. Note that takt time is sometimes used in other meanings but used herein in the meaning of the above-described time. For example, when Nx pieces of a product having a takt time of tXMAX are produced, the production time for the Nx pieces of the product, which is relevant to the delivery deadline, approximates Nx×tXMAX where Nx is sufficiently great.
In conventional factory management, when a production plan is presented, the factory manager makes decisions on running status (starts and stops of operation) and processing conditions of a plurality of machines to produce the products dictated by the production plan by the dictated delivery deadline, and also makes decisions on running status of the air conditioner to achieve required temperature inside the factory, taking into consideration external temperature and temperature changes resulting from running the machines. Working schedule of factory workers is also taken into consideration where the staffing situations affect the range of operational machines.
Contracts between a factory and a power company have a provision on a maximum value of on-peak power supply, with a mandatory curtailment of power supply in the case of demand exceeding the maximum value, which may result in a power failure. In recent years, contracts with power companies also contain a provision that the factories should bring their on-peak power demands even below the maximal value during periods of increased power consumption e.g. during summer, and a violation of the provision may entail a penalty such as raised electricity rates. The difficulty in this case is that factory managers have to consider not only the power consumption in production lines but also power consumption of various factory appliances (e.g., power consumption of office equipment, power consumption of air conditioners in factory offices). The factory managers are responsible for avoiding such a situation and at the same time keeping delivery deadlines and ensuring product qualities. For this reason, conventionally, factory managers are chosen among skilled workers.
However, relying on a limited number of skilled workers for factory management accompanies a lot of risk. To address this, controlling apparatuses have been devised that automatically perform factory production management in accordance with a given production plan by executing factory management program developed on the basis of prevailing factory management experiences.
Japanese Unexamined Patent Publication (Kokai) No. 2011-156598 discloses a power consumption controlling system that includes power monitoring means for machine tools to be controlled and controls rotational acceleration/deceleration rates of the main and feed spindles so that the power consumption of the machine tool may be maintained at not more than a predetermined target value that is changed from time to time.
Japanese Patent Publication No. 5818865 discloses a system for achieving the levelling of power consumption, regarding a production line including a plurality of processes to be carried out by a plurality of line instruments, by making selection of process arrangement combinations based on float periods of processes obtained by the PERT analysis and power consumption per unit period, based on information on each of the processes, and thereby controlling progress of the processes as well as turning off unused line instruments. The above document also discloses that the system measures power consumption in real time, and when power consumption exceeds a predetermined target value, the rotational speed or rotational acceleration/deceleration rate of a motor is reduced.
However, there has been a problem of complicated work and large expenditure involved in developing a factory management program to be installed in an apparatus that performs automatic factory production management.